The present invention relates to a screw separator or a screw press separator for separating solids out of suspensions, the screw separator comprising a housing having a suspension feed pipe, a liquids discharge, and an outlet for the at least partially dewatered solids. These screw separators, often called filter screw presses, are per se known from the prior art.
For example a screw press separator for dewatering solids suspended in water has become known from EP 0 367 037 B1 comprising in a housing a feed pipe to the water to be separated, a discharge pipe for the separated water, and a mouth for the dewatered solid matter. To this end the housing is provided with a strainer basket in which a press screw is arranged. The worm shaft of the press screw protrudes beyond the end of the mouthpiece. In the region of the strainer basket the worm shaft comprises a helical screw or a screw vane the edges of which are positioned close to the inner face of the strainer basket to enable efficient dewatering.
In this known screw press separator a slug forms in front of the mouth during operation and is urged out of the mouth of the screw press separator as a dewatered slug while the solids-free water emerges from the strainer basket, leaving the screw press separator housing. At the same time the slug keeps building up from the solids sediment. To prevent the water from spurting through, a narrow gap must be maintained between the radially outwardly edge of the screw vanes and the strainer basket.
The known screw press separator is reliable in operation. There is the drawback, however, that due to the high stresses the strainer basket must be inspected and possibly replaced on a regular basis.
It is therefore the object of the present invention to provide a screw separator for separating solids out of suspensions which is subjected to reduced wear.